The invention relates to a signal processing device comprising:
a signal source selection means for selecting a signal source from a set of at least two signal sources, the signal from each of the signal sources having at least one controllable parameter, whose value W is defined by a global value G and a local value L associated with a selected signal source, PA1 a control for adjusting the value W, PA1 a storage register for the storage of the global value G, PA1 for each signal source a storage register for the storage of the local value L, PA1 means for obtaining the resultant value W by means of a predetermined combination of G and L. PA1 detection means for determining whether a change .delta.W of W occurs, induced by a change of the setting of the control, within a predetermined time interval .DELTA.T after selection of a signal source, PA1 means adapted to change L by an amount .delta.L and G by an amount .delta.G if .delta.W occurs within .DELTA.T.
Such a signal processing device is known from U.S. Pat. No. 5,046,107. In the known device the controllable parameter referred to each time is the signal strength of the audio signal and the local value is an offset with respect to the global setting of the signal strength. In a given embodiment the known device comprise a separate control for adjusting the local values associated with the selected signal source. This control enables mutual differences in signal volume among the various signal sources to be compensated for. This has the drawback that an additional control element is required and that for each volume correction the user is expected to decide how the correction should be divided between the global volume and the offset value. If the user decides that both values should be corrected, two actions are required.
In another embodiment the known device does not have a separate control for the offset value associated with the selected signal source but the offset value is determined by the master volume control. However, it is not clear how and under what conditions a correction of the master volume control causes a change in the offset value.